This project has three main subdivisions; the first of these is study of the solution structure of DNA and its complexes with small ligands such as polyamines. We propose to determine the rise per base pair of DNA in solution by combined measurement of rotational and translational frictional coefficients using transient electric dichroism and quasielastic light scattering. We will characterize the bundle aggregation of DNA which we recently discovered, and examine the influence of spermine and spermidine on the dichroism and frictional properties of DNA. The second main project area is 5S RNA conformation and protein binding. We will continue the combined use of psoralen crosslinking and RNA sequencing methods to study RNA secondary structure and the site of dimerization. We will examine the influence of ribosomal proteins on the proton-coupled conformational switch of 5S RNA which we recently discovered. Psoralen crosslinking studies to examine the effect of E. coli ribosomal proteins L5, L18 and L25 on RNA secondary structure will also be carried out. The third major project area is the physical properties of chromatin subunits. We will use the electric dichroism method to examin salt-induced folding and unfolding of nucleosomes, (H3-H4)2-DNA complexes, and chromatin fibers. Translational and rotational frictional constants will be measured for chromatin fibers to determine the rise per nucleosome. The dichroism of the fiber will be further characterized to help determine the DNA topology.